The present invention relates to a mooring station and transfer terminal for offshore hydrocarbon production, suitable for mooring oil processing and/or transportation ships.
At the present time offshore hydrocarbon production is developing at locations remote from conventional harbors and this, added to the continuous weight increase of oil tanders, leads to building artificial terminals for mooring oil tankers during loading thereof and/or ships for processing the oil-containing effluent from the producing wells.
Known mooring stations and transfer terminals are connected to a plurality of production underwater wellheads, these terminals comprising a caisson surmounted by at least one rotatable arm which supports at least one pipe for loading oil tankers.
In such prior arrangements the different producing wellheads are connected through pipelines to a production manifold lying on the water bottom, this manifold being connected to the caisson through a gathering line lying on the water bottom and a riser connecting this gathering line to the loading pipe supported by the caisson.
It is also known to provide circulation and safety means through which fluid may circulate during servicing operations on a wellhead, and which provide means for controlling the pressure in the annular space of the producing well.
In the prior art, the various lines and pipes leading from subsurface facilities to surface processing, loading or safety means are often contained within a common riser. For example, such an arrangement is shown in U.S. Pat. No. 3,881,549.
A coaxial safety production pipe is disclosed in U.S. Pat. No. 3,827,486, having a central production pipe and annular, coaxial hydraulic safety valve supply circuits. However, the annular hydraulic circuits do not communicate between separate manifolds and surface facilities. Rather, they serve to seal off the well in the event of damage to the casing.